Around 20,000 people may have been exposed to measles at a large religious event in Kentucky, the federal Centers for Disease Control and Prevention and said.

In a statement to the Guardian, the CDC said it was “aware of a confirmed case of measles in an unvaccinated and contagious individual who attended a large religious gathering in Kentucky on 17 and 18 February.

“Large numbers of people that attended the gathering from across Kentucky and from other states and countries may have been exposed.